Process for making alkali metal aluminate



April 3, 1945. E. E. FISHER 2, 7

7 PROCESS FOR MAKING ALKALI METAL ALUMINATES Filed Aug. 1, 1941 "640/CARBo/v Na CZ Ca, C0

FURNACE To FORM fNfER 50/1. IN WA 7351a Ca C0 FUR NACE L/X/v/ATE WITHCOOL WATER FILTER FILTER HEAT 4 AL 0 3/1 0 Another object of myinvention is to provide an Patented Apr. 3, 1945 UNITED STATES PATENTOFFICE PROCESS FOR/MAKING ALKALI LIETAL ALUMINATE Elbert n. Fisher, ,St.Louis, MO., assignor to Mar-- lew W. Fisher, St. Louis, Mo.

Application August '1, 1941, Serial No. 404,972

7 Claims.

improved method of making soluble sodium aluminate from an aluminousmaterial, which process can be carried on in a continuous manner and byemploying raw material having either a low or a high percentage ofalumina or a mixture of both.

Still another object of my invention is to pro-- vide a new processwhereby substantially the total amount of alumina in the aluminousmaterial can be recovered without its being contaminated with othersubstances, particularly silica or compounds thereof, iron, titanium andso forth.

A more general object of my invention is to provide a simple andeconomical method whereby commercially usable alumina may be recoveredfrom cheap and readily available raw material,

Yet another object of my invention is to so provide an improved methodof obtaining a so]- uble aluminum salt from an aluminous material thatother salts can also be readily created from -.,the vehicle employed toprovide the solubility of the aluminum salt.

' The accompanying drawing shows a fiow sheet {of the process embodyingmy invention.

.In using this improved process, the material tobe used is ground fineand mixed with pow"- .dered coal, powdered limestone, soda chloride, in

presence of sufiicient water to make a still paste, which is then placedin a revolving furnace where it first slowly dried, leaving the' mixedmaterials" in the form of unevenly sized lumps, pass n them into thehotter zone of the furnace where the mixture ls subiected to a heat notto exceed atemperature of 1750 F; for five hours.

Thisheat may be produced from coal, gas, oilor whatever style is deemedbest, and is mixed with steam or water vapor, and is desirably a neutralrather than an oxidizing flame. The gases: evolved are conducted througha chamber otlimest'one in lumps which are continuously wet with water,creating a solution of calcium chloride.-;;-; Y

. When the mixed raw materials have passed through the furnace, they areplaced in a receptacle, covered with water, and boiled for a limitedtime, then dried, mixed with a mixture 01' calcium carbonate andammonium chloride, and again passed through a rotating furnace heated toa dull red heat of about 1350 F. The resulting product is thenlixiviated with water to create a dilute solution. This may beevaporated to form sodium aluminate or be kept in solution to beimpregnated with whatever gas it is'to be deemed desirable, as forinstance, when sodium V sulfide is desired, the hydrogen sulfide gas ispassed through the soda aluminate solution, during which time the gasreacts with'the sodium which is the vehicle causing the alumina toremain in solution. Deprived of this vehicle, the alumina is instantlyprecipitated as alumina hydroxide, A1203.3H2O., The sodium then becomesat first a sodium hydroxide, then changing to sulfide as largerquantities of the gas are passed through the solution, eventuallybecoming sodium sulfide plus water of crystallization NaaS plusA12O3.3H2O. When commercially prepared, the sodium sulfide may be fusedor crystallizedwhile the alumina may be dried as the hydroxide or heatedand burned to form the oxide.

In place of hydrogen sulfide being used to form the sulfide, the sulfitemay be obtained as well as other salts of sodium.

As an illustration of the process, the following materials withapproximate amounts used are mixed with a little water.

Pounds Clay 160 Coal e 30 Sodium chloride 320 Limestone r heatedslowly-to 1750 F. for about 5 hours, placed in a receptacle, coveredwith water, and boiled, dried, mixed with 10 pounds of a mixture ofcalcium carbonate and ammonium chloride in the proportion of 6 ofcalcium to 1 of ammonia and heatedto'approximately 1350 F. for an hour6r two. This is then lixiviated in water.

This watery solution is then evaporated or carried out ready for furtheruse. As a further example such as the manufacture of sodium su1- flde,the hydrogen sulfide is discharged into gas towers in which sprays ofthe sodium aluminate arepassing. The solution, now containing varyingqualities of the aluminate, the sodium sulfide and alumina, falls,through filters which separate the alumina as fast as made. The aluminais retained while the clear, weakened so- The material resulting fromthe first step. i.. e. that which is removed from the furnace which hasbeen heated to 1750 F. consists of both sodium aluminate and aninsoluble so-called sodium silico aluminate with silicic acid, as wellas calcium oxide, calcium silicate and the impurities. When this isplaced in water and boiled, the completed sodium aluminate is formed andsimultaneously freed from the other material. There is also present anexcess of sodium, and this is. converted into the hydroxide by reactingwith the calcium oxide present. Thus there is obtained in solutionalumina in excess of that combined with sodium in the sintered mixture.some of the um silico aluminate with the silicic acid combines with thesodium hydroxide,

. and as the mass is slowly dried the silicic acid becomes eventually,as the heat is increased, silica, and the rest of the silica combineswith the calcium in the presence of ammonium chloride to become calciumsilicate, so that when added to water there is present traces of calciumchloride, 7

calcium oxide, silica and the other impurities, with sodium aluminate insolution. This is largely due to the tripleeffect of the sodium. The"alumina present in the so-called sodium silico aluminate has first beenacted upon by the sodium hydroxide while in solution, next by the samesodium hydroxide in the dried then'heated asvaaio aInaproeessiorobtainingaluminafrcman' siliceousmaterial, the stepscomprisingbcllinginwateraslnteredmixtureostbematerialcontainingasodiumoxidetoobtainin'so--luticualuininainexcessoi!thatcomlziincdwith soluble calcium silicate tothereby permit thesilica to be separated from the sodium aluminate byfiltering. v 3. Aprocessoitreatingaluminoussiliceousmaterial. whichcomprises heating the material and a sodium compound was calciumcompound to approximately 1750 degrees Fahrenheit to form calciumsilicate and sodium oxide, boiling the mixture in water to place thealumina in solution together with'alumina not already united with sodiumin the heating'step, and then creat- .form, while afterwards by thissame sodium m an sodium silico aluminate is now soluble sodium aluminateand insoluble silica, as it has been found that the processes heretoforeused have been contaminated with silicic acid in the ortho form, H4Si04and which has not been separated; while withthe above described tripleeiiect method, means have been found to segregate this silicic acid,recovering a large portion of the herealumina, as this form of silicicacid is soluble in alkalies and rendered insoluble when heated to a dullred heat with ammonia chloride and calcium carbonate. While there ispresent during the latter portion of the process, sodium, alumina 1 andsilica, all in the soluble form, the method when closing tmansposes thesilica toithe insoluble form without disturbance to the sodium and thealumina which are combined, forming sodium aluminate. This is thendissolved in water, filtered, and, if used for sodium sulfide or othersodium salts is in the solution ready for use.

' tain in solution alumina in excess 0! that combined'withthe alkali 'inthesintered'mixture -and'the addlngto the resulting mixture ammoniumchloride and available calcium' and the heating thereof, to atemperature giving a dull red color to cause substantially all thesoluble silica-'icompounds to become insoluble by uniting with the tothereby permit the silica to .be separated from the aluminate toforelost percentage of possible convertible in an insoluble calcium silicateb adding ammonium chloride and calcium carbonate and subiecting to suchtemperature that the mixture will have a dull red glow.

4. A process of treating aluminous ailiceom material; which comprisessintering a mlxturecon taining the miterial, calcium carbonate and asodium compound, boiling the mixture in water to obtain in solutionumina in' excess oi that combined with the sodium in the sinteredmixture, and adding to the resulting mixture ammonium chloride andavailable calcium and heating :Iliereoi l to approximately 1350 degreesl'ahren e t. -5. A process oi treating aluminous siliceous materialwhich comprises sinteringa mixture containing the material, calciumcarbonate, a

sodium compound; and carbon, boiling said mixture in water to bbtain insolution alumina in and then lixiviating the resulting substance withwater to obtain sodium aluminate.

6. A process. of treating aluminous siliceous material which mixingtogether with a quantity of the material approximately twice'as muchsodium compound than the material and a less quantity of calciumcarbonate than the material, sintering the mixture, boiling in water toobtain in solution alumina in excess oi that combined with the sodium inthe sintered mixture, drying the mixture, adding thereto ammoniumchlorideand calcium carbonate, subjecting theresulting mixture to atemperature not to free sodium aluminate without contamination by silicaor its compounds.

7. In a processof treating alu'minous siliceous material which comprisessintering a mixture containing the material, calcium carbonate and asodium compound, adding to the resulting mixture ammonium chloride andcalcium carbonate,

heating the resulting mixture toatemperature approximating 1350 degreesFahrenheit, and then separating the resulting substance to free sodiumaluminate. v

mm'r E. FISHER.

